The invention relates to a combined steering angle and torque sensor that inductively and with eddy current damping generates two absolute angle measurement signals over an angle range of 360 degrees.
For such measurements the steering column is normally divided by a torsion element at an abutment. The input shaft faces the steering wheel and bears a first actuating element in the vicinity of the twisted abutment. The output shaft of the steering column is associated with the steering gear and bears a second actuating element in the vicinity of the twisted abutment.
In this technical context, known in the prior art are (i) an inductive measurement technique by means of eddy current damping, (ii) measurement planes perpendicular to the axis of rotation, and (iii) two annular disk-shaped electrical damping members that are attached to the steering column on both sides of the torsion element; see the prior art in accordance with DE 29 51 148 C2, DE 37 29 230 C2, DE 101 01 174 B4, DE 199 41 464 A1, DE 101 56 238 A1, and DE 10 2004 027 954 A1. Known from one or the other of these publications are also (iv) two angle sensors, that are independent of one another, in two measurement planes, (v) a plurality of flat coils in one measurement plane, and (vi) flat coils that are not only staggered radially, but are also arrayed along the circumference over 360 degrees. In patent DE 101 01 174 B4, the elastic element is arranged outside of the longitudinal axis of the steering column, specifically on the steering wheel.
In the fields of automobiles, trucks, and commercial vehicles, in the past the steering angle and the torque have been detected using two separate sensors that have different principles of functioning (inductive, optical, capacitive, magnetic, etc.). Based on the high resolution that is required, many of the current torque sensors permit only a small torque range that is expressed as an angle on the order of magnitude of +/−10 degrees. In many multiturn sensors the steering angle range is also determined by the required accuracy and is often limited. Redundancy is increasingly demanded because these sensors are used in safety-related applications. Frequently a larger amount of space is required overall.
The object of the invention is comprised in providing a combined sensor in a small space despite the redundancy and steering angle/torque dual function.